Uniform Circular Motion Part 2 Worked Examples

Question 1 A merry-go-round takes 15s to complete one revolution. What is the angular velocity? How does the speed of the horses vary from the inside at a radius of 5m and the outside radius 10 m?

Question 2 A DVD spins at 650 revolutions per minute. What is the speed at a point 3.5cm from the centre of the disk?

Question 3 The diagram below shows a dust particle at position D on a rotating vinyl disc. A combination of electrostatic and frictional forces act on the dust particle to keep it in the same position. The dust particle is at a distance of 0.125 m from the centre of the disc. The disc rotates at 45 revolutions per minute. (a) Calculate the linear speed of the dust particle at D. b) (i) Mark on the diagram above an arrow to show the direction of the resultant horizontal force on the dust particle. (ii) Calculate the centripetal acceleration at position D. (c) On looking closely at the rotating disc it can be seen that there is more dust concentrated on the inner part of the disc than the outer part. Suggest why this should be so.

a) Calculate the linear speed of the dust particle at D.

b) (i) Mark on the diagram above an arrow to show the direction of the resultant horizontal force on the dust particle. ii) Calculate the centripetal acceleration at position D.

(c) On looking closely at the rotating disc it can be seen that there is more dust concentrated on the inner part of the disc than the outer part. Suggest why this should be so.